An individual polymer molecule (artist’s impression) can wriggle out of a pack of similar molecules. Credit: Juan Gaertner/Science Photo Library When densely packed, long molecular chains, such as chromosomes, in living cells can crawl past their neighbours, computer simulations and theoretical modelling suggest1. Access Nature and 54 other Nature Portfolio journals Get Nature+, our best-value online-access subscription $32.99 / 30 days cancel any time Subscribe to this journal Receive 51 print issues and online access $199.00 per year only $3.90 per issue Rent or buy this article Prices vary by article type from$1.95 to$39.95 Prices may be subject to local taxes which are calculated during checkout doi: https://doi.org/10.1038/d41586-026-00767-7 Höfler, A. H. T. P., Chubak, I., Likos, C. N. & Smrek, J. Phys. Rev. X 16, 011046 (2026).…